interleukin-8 and prolyl-glycyl-proline

Persistent neutrophilia is implicated in the pathology of several chronic lung diseases and consequently targeting the signals that drive the recruitment of these cells offers a plausible therapeutic strategy. The tripeptide Pro-Gly-Pro (PGP) is a neutrophil chemoattractant derived from extracellular matrix collagen and implicated in diseases such as COPD and cystic fibrosis. It was anticipated that PGP exerts its chemoatactic activity by mimicking key sequences found within classical neutrophil chemokines, such as CXCL8, and binding their receptors, CXCR1/2. Recently, however, the role of CXCR1/2 as the receptors for PGP has been questioned. In this issue of European Journal of Pharmacology, three studies address this controversy and demonstrate CXCR1/2 to be a common receptor for CXCL8 and PGP. Accordingly, these studies demonstrate the therapeutic potential of targeting this shared receptor to simultaneously alleviate neutrophilic inflammation driven by multiple neutrophil chemoattractants.

Topics: Acetylation; Chronic Disease; Humans; Interleukin-8; Lung Diseases; Molecular Targeted Therapy; Neutrophils; Oligopeptides; Proline; Receptors, CXCR

Cigarette smoking induces inflammatory responses in all smokers and is the major risk factor for lung disease such as chronic obstructive pulmonary disease (COPD). In this progressive disease, chronic inflammation in the lung contributes to lung tissue destruction leading to the formation of chemotactic collagen fragments such as N-acetylated Proline-Glycine-Proline (N-ac-PGP). The generation of this tripeptide is mediated by a multistep pathway involving matrix metalloproteases (MMPs) 8 and 9 and prolyl endopeptidase (PE). Here we investigated whether cigarette smoke extract (CSE) stimulates human PMNs to breakdown whole matrix collagen leading to the generation of the chemotactic collagen fragment N-ac-PGP.. Incubating PMNs with CSE led to the release of chemo-attractant CXCL8 and proteases MMP8 and MMP9. PMNs constitutively expressed PE activity as well as PE protein. Incubating CSE-primed PMNs with collagen resulted in collagen breakdown and in N-ac-PGP generation. Incubation of PMNs with the tripeptide N-ac-PGP resulted in the release of CXCL8, MMP8 and MMP9. Moreover, we tested whether PMNs from COPD patients are different from PMNs from healthy donors. Here we show that the intracellular basal PE activity of PMNs from COPD patients increased 25-fold compared to PMNs from healthy donors. Immunohistological staining of human lung tissue for PE showed that besides neutrophils, macrophages and epithelial cells express PE.. This study indicates that neutrophils activated by cigarette smoke extract can breakdown collagen into N-ac-PGP and that this collagen fragment itself can activate neutrophils, which may lead in vivo to a self-propagating cycle of neutrophil infiltration, chronic inflammation and lung emphysema. MMP-, PE- or PGP-inhibitors can serve as an attractive therapeutic target and may open new avenues towards effective treatment of COPD.

Topics: Aged; Case-Control Studies; Cell Survival; Collagen; Collagen Type I; Female; Humans; Inflammation; Interleukin-8; Leukocytes, Mononuclear; Lung; Male; Matrix Metalloproteinase 8; Matrix Metalloproteinase 9; Middle Aged; Neutrophils; Oligopeptides; Proline; Prolyl Oligopeptidases; Pulmonary Disease, Chronic Obstructive; Serine Endopeptidases; Smoking; Tobacco Products

Keratinocytes are the predominant cell type in epidermis, and are primarily responsible for the epithelialization phase of wound healing. Previous studies by our group showed a positive correlation between IL-8 concentration and delayed healing of porcine cutaneous partial-thickness wounds. Interleukin-8 and collagen-breakdown product N-acetyl-Pro-Gly-Pro (PGP) are known as chemoattractant molecules for neutrophils during inflammation. The activity of both molecules is dependent on chemokine receptors CXCR1 and CXCR2. In addition to neutrophils, keratinocytes also express CXCR1 and CXCR2. Here we investigated the effects of IL-8 and PGP on keratinocyte proliferation and migration. Our results showed that IL-8 up to 100 ng/mL does not have any significant impact on keratinocyte proliferation or migration. ECM-derived tripeptide PGP chemotactically attracts neutrophils but not keratinocytes. PGP strongly inhibits keratinocyte proliferation and migration in a cell-type specific manner. Thus, collagen breakdown product PGP plays a key role in modulating both the inflammatory and epithelialization phases of wound healing.

Topics: Cell Movement; Cell Proliferation; Cells, Cultured; Chemotaxis, Leukocyte; Dose-Response Relationship, Drug; Extracellular Matrix; Fibroblasts; Humans; Interleukin-8; Keratinocytes; Neutrophils; Oligopeptides; Proline; Receptors, Interleukin-8A; Receptors, Interleukin-8B; Wound Healing

Lung transplantation is a therapeutic modality frequently used in end-stage lung disease. Unfortunately, lung transplant recipients have poor clinical outcomes, often due to the development of bronchiolitis obliterans syndrome (BOS). This process is often characterized by the pathologic findings of obliterative bronchiolitis: neutrophil influx and extracellular matrix remodeling leading to luminal obstruction and airway inflammation. The molecular mechanisms underlying BOS are poorly understood and disease-specific biomarkers are lacking. We report that in addition to increased levels of IL-8, the level of the neutrophil chemoattractant proline-glycine-proline (PGP) is elevated in BOS patient bronchoalveolar lavage (BAL) fluid. The enzymes responsible for generating PGP, matrix metalloproteases 8 and -9 and prolyl endopeptidase, are also elevated in these samples. Together, IL-8 and PGP account for most of the neutrophil chemoattractant capacity seen in BOS BAL fluid. Using specific neutralizing Abs to both IL-8 and PGP, we demonstrate that PGP is a prominent neutrophil chemoattractant found in BAL fluid from individuals at the time of diagnosis of BOS. These findings highlight the influence of a matrix-derived neutrophil chemoattractant in posttransplantation BOS and provide opportunities for the development of unique diagnostics and therapeutics to potentially improve disease outcomes.

Topics: Biomarkers; Blotting, Western; Bronchiolitis Obliterans; Bronchoalveolar Lavage Fluid; Chemotaxis, Leukocyte; Enzyme-Linked Immunosorbent Assay; Female; Graft Rejection; Humans; Interleukin-8; Lung Transplantation; Male; Matrix Metalloproteinase 8; Matrix Metalloproteinase 9; Middle Aged; Neutrophils; Oligopeptides; Proline